1. Field of the Invention
The present invention relates to computer software, and deals more particularly with techniques for building distributed software services as aggregations of other services.
2. Description of the Related Art
The popularity of distributed computing networks and network computing has increased tremendously in recent years, due in large part to growing business and consumer use of the public Internet and the subset thereof known as the “World Wide Web” (or simply “Web”). Other types of distributed computing networks, such as corporate intranets and extranets, are also increasingly popular. As solutions providers focus on delivering improved Web-based computing, many of the solutions which are developed are adaptable to other distributed computing environments. Thus, references herein to the Internet and Web are for purposes of illustration and not of limitation.
The early Internet served primarily as a distributed file system in which users could request delivery of already-generated static documents. In recent years, the trend has been to add more and more dynamic and personalized aspects into the content that is served to requesters. One area where this trend is evident is in the increasing popularity of content frameworks such as those commonly referred to as “portals” (or, equivalently, portal platforms, portal systems, or portal servers). A portal is a type of content framework which is designed to serve as a gateway, or focal point, for end users to access an aggregation or collection of information and applications from many different sources. Portals are typically visual in nature, and provide their users with a Web page known as a “portal page”. A portal page is often structured as a single overview-style page (which may provide links for the user to navigate to more detailed information). Alternatively, portal pages may be designed using a notebook paradigm whereby multiple pages are available to the user upon selecting a tab for that page. Some experts predict that portal pages will become the computing “desktop” view of the future.
Another area where advances are being made regarding dynamic content is in the so-called “web services” initiative. This initiative is also commonly referred to as the “service-oriented architecture” for distributed computing. Web services are a rapidly emerging technology for distributed application integration in the Internet. In general, a “web service” is an interface that describes a collection of network-accessible operations. Web services fulfill a specific task or a set of tasks. They may work with one or more other web services in an interoperable manner to carry out their part of a complex workflow or a business transaction. For example, completing a complex purchase order transaction may require automated interaction between an order placement service (i.e. order placement software) at the ordering business and an order fulfillment service at one or more of its business partners.
Many industry experts consider the service-oriented web services initiative to be the next evolutionary phase of the Internet. With web services, distributed network access to software will become widely available for program-to-program operation, without requiring intervention from humans.
Web services are generally structured using a model in which an enterprise providing network-accessible services publishes the services to a network-accessible registry, and other enterprises needing services are able to query the registry to learn of the services' availability. The participants in this computing model are commonly referred to as (1) service providers, (2) service requesters, and (3) service brokers. These participants, and the fundamental operations involved with exchanging messages between them, are illustrated in FIG. 1. The service providers 100 are the entities having services available, and the registry to which these services are published 110 is maintained by a service broker 120. The service requesters 150 are the entities needing services and querying 140 the service broker's registry. When a desired service is found using the registry, the service requester binds 130 to the located service provider in order to use the service. These operations are designed to occur programmatically, without human intervention, such that a service requester can search for a particular service and make use of that service dynamically, at run-time. The web services model is theoretically available for any type of computing application. However, the web services which are accessible from registries today are limited to relatively simple programs such as “Hello, World!” demo programs, programs which look up the current temperature for a particular zip code, programs which perform currency exchange calculations, and so forth.
The core set of standards on which web services work is being built includes HTTP (“Hypertext Transfer Protocol”), SOAP (“Simple Object Access Protocol”) and/or XML (“Extensible Markup Language”) Protocol, WSDL (“Web Services Description Language”), and UDDI (“Universal Description, Discovery, and Integration”). HTTP is commonly used to exchange messages over TCP/IP (“Transmission Control Protocol/Internet Protocol”) networks such as the Internet. SOAP is an XML-based protocol used to send messages for invoking methods in a distributed environment. XML Protocol is an evolving specification of the World Wide Web Consortium (“W3C”) for an application-layer transfer protocol that will enable application-to-application messaging, and may converge with SOAP. WSDL is an XML format for describing distributed network services. UDDI is an XML-based registry technique with which businesses may list their services and with which service requesters may find businesses providing particular services. (For more information on SOAP, refer to “Simple Object Access Protocol (SOAP) 1.1, W3C Note 08 May 2000”, which is available on the Internet at http://www.w3.org/TR/2000/NOTE-SOAP-20000508. See http://www.w3.org/2000/xp for more information on XML Protocol and the creation of an XML Protocol standard. The WSDL specification is titled “Web Services Description Language (WSDL) 1.1, W3C Note 15 Mar. 2000”, and may be found on the Internet at http://www.w3.org/TR/2001/NOTE-wsd1-20010315. For more information on UDDI, refer to the UDDI specification which is entitled “UDDI Version 2.0 API Specification, UDDI Open Draft Specification 8 Jun. 2001”, and which can be found on the Internet at http://www.uddi.org/specification.html. HTTP is described in Request For Comments (“RFC”) 2616 from the Internet Engineering Task Force, titled “Hypertext Transfer Protocol—HTTP/1.1” (June 1999).)
Application integration using these open standards requires several steps. The interface to a web service must be described, including the method name(s) with which the service is invoked, the input and output parameters and their data types, and so forth. WSDL documents provide this information, and are transmitted using a UDDI publish operation to a registry implemented according to the UDDI specification. Once the service is registered in the UDDI registry, service requesters can issue UDDI find requests to locate distributed services. A service requester locating a service in this manner then issues a UDDI bind request, which dynamically binds the requester to the located service using the service information from the WSDL document. (These UDDI operations have been illustrated, at a high level, in FIG. 1.) SOAP/XML Protocol and HTTP messages are commonly used for transmitting the WSDL documents and the UDDI requests. (Hereinafter, references to SOAP should be construed as referring equivalently to semantically similar aspects of XML Protocol. Furthermore, it should be noted that references herein to “HTTP” are intended in a generic sense to refer to HTTP-like functions. Some UDDI operations, for example, require HTTPS instead of HTTP, where HTTPS is a security-enhanced version of HTTP. These differences are not pertinent to the present invention, however, and thus no distinction is made hereinafter when discussing HTTP.)
The goal of web services is to provide service requesters with transparent access to program components which may reside in one or more remote locations, even though those components might run on different operating systems and be written in different programming languages than those of the requester. While a significant amount of work has been done to define the goals, architecture, and standards on which web services will be based, much work remains to be done to make web services operate effectively and efficiently.